Hundreds of different ingredients are used in commercial pet foods, so it’s no surprise that some of them are not well received by the animals eating them.

Food allergies may cause vomiting, diarrhea, pruritis or skin eruptions. However, a reaction to food doesn’t necessarily indicate an allergy. Many pets have a food sensitivity or intolerance, but relatively few are truly allergic.

Food allergies

A food allergy is an immune reaction (usually a Type I hypersensitivity reaction) to a particular protein; signs are manifested in either the gastrointestinal tract or skin. Experts believe that between 10% and 30% of all food reactions are allergic. In dogs, a similar percentage of ear infections have an allergic component. However, up to 50% of feline ear infections may be caused by food allergies.

Food hypersensitivities tend to develop over long periods (months to years) in response to foods or treats the pet eats frequently. Food allergies are uncommon in pets under one year of age. Common proteins, and therefore common allergens, include the following:

• Beef • Chicken • Fish (cats) • Dairy • Wheat • Corn • Soy • Eggs

Food allergies may cause extreme pruritis on their own, but secondary infections with bacteria and yeast are also very common. However, allergic skin disease is far more commonly associated with atopy, fleabite hypersensitivity, or other causes.

Food intolerance

Food intolerance usually causes local reactions in the gastrointestinal system. A pet experiencing signs related to food may be sensitive or intolerant to one main ingredient, or to one or more of the colorings, preservatives, texturizers, palatability enhancers, or other substances in any of the 27 categories of allowable pet food additives. Food intolerances can occur at any age and involve any ingredient.

Corn, wheat and soy contain protein, which can produce allergies; but it’s more likely that pets are sensitive to these ingredients rather than truly allergic to them. One factor that could be contributing to this is that more than 80% of corn and 95% of soy grown in the US is genetically modified (GM). Such crops are likely to contain higher levels of pesticide residue. Crops rejected for human consumption due to excessive residues can still be used in animal feed and pet food. The potential for reaction is obvious; but the ultimate and cumulative effects of GM products are as yet unknown.

Many pet foods, particularly mega-brands (including foods specifically promoted to veterinarians), store brands, and less expensive foods contain high protein grain extracts, such as wheat gluten, which is used to create shapes (such as “slices” or “chunks”) or as a thickener. Many dry foods include corn gluten meal, which contains 60% protein and is used as a substitute for more expensive animal protein. This is inappropriate for carnivorous pets, particularly cats, which do best on a high protein, high moisture, low carbohydrate diet.

Treating sensitivities

1. For food allergies, a full diet trial is warranted to determine the allergy-causing ingredient/s. The pet is exclusively fed one “novel ingredient” or hypoallergenic food for eight to 12 weeks. The choice of ingredient or food depends on what the pet has been eating in the past. Note that cross-reactions may occur; e.g., pets allergic to chicken may also react to chicken eggs, as well as other poultry meats.

Alternative proteins include venison, rabbit, duck, bison, emu, ostrich, kangaroo or beaver. Pets already eating a single-protein food may do fine on different proteins like fish, lamb or turkey, even if they are common in other foods. However, research has found cross-contamination of several “single-ingredient” OTC foods (both dry and canned) with common allergens. If your client is using an OTC food with no response, a purified or veterinary diet may be more successful. Some animals do better on the canned version of a particular food. They may be reacting to heat-denatured proteins in the dry food; canned foods are processed at lower temperatures.

Also opt for novel carbohydrate sources (since all carb sources contain some protein), such as green peas, white potatoes, sweet potatoes, rice, quinoa or barley.

When choosing the trial food, note that “poultry” may include chicken, turkey, duck, quail or other fowl. “Meat” is usually beef, but may legally include pork, lamb and goat. “Meat by-products” or “meat and bone meal” may contain any mammal species. It’s best to choose a food with specifically named single ingredients.

Digestive signs often resolve quickly, but skin reactions tend to be far more persistent. If the skin does clear up, the pet can be challenged with one ingredient at a time to determine which ingredient/s caused the problem.

Many people have had great success using raw meat-based and homemade diets. A wide variety of meats are now available online as well as locally. It should be noted that many animals that are allergic to a particular protein in processed food do very well with the raw or very lightly cooked version of the same protein.

Clients must understand that a diet trial includes only the test food and water. Just one slip (such as giving a treat or supplement containing beef liver to a beef-allergic pet) could put the trial back to square one. Results may not be seen for up to eight weeks, so caution clients that total compliance, as well as patience, will be needed.

2. The treatment for food intolerance is much simpler. Changing the brand or flavor of food may be all that’s needed to resolve the problem, although it may take trying a few different brands or flavors to hit upon the right one. GI signs typically diminish or disappear within days once the offending ingredient is removed. Clients should understand that these animals frequently respond favorably to a novel or limited ingredient diet, even when no allergy is present. To maximize success, choose good quality natural foods without artificial additives, or try a homemade diet or raw diet. Canned food may provide better results, as it typically contains fewer additives and preservatives.

Preventing problems

Variety is a major key to preventing food allergies and intolerances. Remember, food allergies develop when a pet eats the same ingredients over a long period of time. Pets that develop an allergy to one food are likely to eventually react to other foods, so protein sources should be changed at least every three months.

If the pet is eating dry food, make the switch gradually over a week or two, so colonic bacteria have time to adjust; too fast a change can cause diarrhea. Recommend high quality natural foods that don’t contain unspecified meat, liver or other protein sources, chemical preservatives such as BHA, BHT or ethoxyquin, or other artificial additives. High quality natural foods tend to contain better quality ingredients that are less likely to cause an adverse reaction. Canned foods tend to cause fewer reactions than dry foods. For cats, once they are accustomed to variety, brands and flavors may be changed daily. Feeding a variety of foods also provides an added bonus: it prevents finicky behavior.

Lastly, remember that stress plays a big role in many health issues, especially those involving the digestive and immune systems. Flower essences and herbs can be valuable aids here. Remind clients that pets need “quality time” every day. Exercise is nature’s greatest stress-reducer, so encourage clients to get out there and walk the dog, or enjoy daily interactive play sessions with the cat. Less stress also means fewer behavior problems, so it’s a win-win for all.

Jean Hofve, DVM, earned her Doctor of Veterinary Medicine at Colorado State University. In addition to conventional veterinary training, she studied veterinary homeopathy, homotoxicology, Reiki, and other holistic modalities. She has researched pet food and feline nutrition for nearly two decades, and is an expert on holistic pet health and the commercial pet food industry. She is an official advisor to AAFCO, the organization that sets pet food rules and standards in the U.S. and Canada. Dr. Hofve co-authored the book Holistic Cat Care.

Supplements for sensitivities

• Digestive enzymes: Can be given with food to help break down proteins and other compounds more completely, so they are less likely to trigger an adverse reaction or immune response. • Probiotics: Help keep the gut bacteria nourished and balanced; they also appear to have anti-inflammatory properties. • Omega-3 fatty acids (purified marine source): Are naturally anti-inflammatory, as well as important for skin healing. The intestinal epithelium may also benefit from Omega-3 supplementation.

A food allergy is an immune reaction (usually a Type I hypersensitivity reaction) to a particular protein; signs are manifested in either the gastrointestinal tract or skin.

Food intolerance usually causes local reactions in the gastrointestinal system.